Customized patient-specific orthopaedic surgical instrument

ABSTRACT

An orthopaedic surgical instrument includes a customized patient-specific surgical instrument having a body. A cutting guide slot extends through the body. A pair of first arms extends posteriorly from the body. Each arm includes a first customized patient-specific negative contour configured to receive a portion of a first corresponding positive contour of one of a patient&#39;s femoral condyles. A second arm extends proximally from the body. The second arm has a second customized patient-specific negative contour configured to receive a portion of a second corresponding positive contour of an anterior surface of the patient&#39;s femur. A method of performing a surgical procedure is also disclosed.

TECHNICAL FIELD

The present disclosure relates generally to orthopaedic surgical instruments and, more particularly, to customized patient-specific orthopaedic surgical instruments.

BACKGROUND

Joint arthroplasty is a well-known surgical procedure by which a diseased and/or damaged natural joint is replaced by a prosthetic joint. For example, in a total knee arthroplasty surgical procedure, a patient's natural knee joint is partially or totally replaced by a prosthetic knee joint or knee prosthesis. A typical knee prosthesis includes a tibial tray, a femoral component, and a polymer insert or bearing positioned between the tibial tray and the femoral component. In a hip replacement surgical procedure, a patient's natural acetabulum is replaced by a prosthetic cup and a patient's natural femoral head is partially or totally replaced by a prosthetic stem and femoral ball.

To facilitate the replacement of the natural joint with a prosthesis, orthopaedic surgeons use a variety of orthopaedic surgical instruments such as, for example, cutting blocks, drill guides, milling guides, and other surgical instruments. Typically, the orthopaedic surgical instruments are reusable and generic with respect to the patient such that the same orthopaedic surgical instrument may be used on a number of different patients during similar orthopaedic surgical procedures.

The orthopaedic surgical instruments may also be customized to a specific patient. Such “customized patient-specific orthopaedic surgical instruments” are single-use surgical tools for use by a surgeon in performing an orthopaedic surgical procedure that is intended, and configured, for use on a particular patient. It should be appreciated that these instruments are distinct from standard, non-patient-specific orthopaedic surgical instruments that are intended for use on a variety of different patients. These customized patient-specific orthopaedic surgical instruments are distinct from orthopaedic prostheses, whether patient-specific or generic, which are surgically implanted in the body of the patient. Rather, customized patient-specific orthopaedic surgical instruments are used by an orthopaedic surgeon to assist in the implantation of orthopaedic prostheses.

SUMMARY

According to an aspect of the disclosure, an orthopaedic surgical instrument includes a customized patient-specific surgical instrument having a body. A cutting guide slot extends through the body. A pair of first arms extends posteriorly from the body. Each arm includes a first customized patient-specific negative contour configured to receive a portion of a first corresponding positive contour of one of a patient's femoral condyles. A second arm extends proximally from the body. The second arm has a second customized patient-specific negative contour configured to receive a portion of a second corresponding positive contour of an anterior surface of the patient's femur. An alignment slot extends through the body and the proximally extending arm and is positioned to align with a deepest portion of a trochlear groove of the patient's femur when the customized patient-specific surgical instrument is positioned on the patient's femur.

In some embodiments, the alignment slot may extend transverse to the cutting guide slot.

In some embodiments, the body may have a planar distal surface and a planar proximal surface. The alignment slot may include an opening extending through the distal surface and an opening extending through the proximal surface.

In some embodiments, the second arm may include a trunk extending from the body and a flange attached to a proximal end of the trunk. The flange may include a portion of the second customized patient-specific negative contour. The trunk may include an anterior surface and a posterior surface. The alignment slot may include an opening extending through the anterior surface and an opening extending through the posterior surface. The opening extending through the anterior surface and the opening extending through the posterior surface may be curved.

In some embodiments, the customized patient-specific surgical instrument may include a boss attached to, and extending from, the body to a free end spaced apart from the body. The boss may include an opening that is defined in its free end. A guide hole may extend through the boss.

According to another aspect of the disclosure, an orthopaedic surgical instrument includes a customized patient-specific surgical instrument having a body. A cutting guide slot may extend through the body. A pair of first arms may extend posteriorly from the body. Each arm may include a first customized patient-specific negative contour configured to receive a portion of a first corresponding positive contour of one of a patient's femoral condyles. An alignment slot may extend through the body transverse to the cutting guide slot and is positioned to align with a deepest portion of a trochlear groove of the patient's femur when the customized patient-specific surgical instrument is positioned on the patient's femur.

In some embodiments, the body may have a planar distal surface and a planar proximal surface. The alignment slot may include an opening extending through the distal surface and an opening extending through the proximal surface.

In some embodiments, the customized patient-specific surgical instrument may include a boss attached to, and extending from, the body to a free end spaced apart from the body. The boss may include an opening that is defined in its free end. A guide hole may extend through the boss.

In some embodiments, a second arm may extend proximally from the body. The second arm may include a trunk extending from the body and a flange attached to a proximal end of the trunk. The second arm may have a second customized patient-specific negative contour configured to receive a portion of a second corresponding positive contour of an anterior surface of the patient's femur. The flange may include a portion of the second customized patient-specific negative contour. The trunk may include an anterior surface and a posterior surface. The alignment slot may include an opening extending through the anterior surface and an opening extending through the posterior surface. The opening extending through the anterior surface and the opening extending through the posterior surface may be curved.

According to yet another aspect of the disclosure, a method of performing an orthopaedic surgical procedure includes placing a visual marking on a surface defining a deepest portion of a trochlear groove of a patient's femur. The method also includes placing a customized patient-specific surgical instrument on the patient's femur. The method also includes aligning an alignment slot extending through the customized patient-specific surgical instrument with the visual marking on the surface of the patient's femur to position the customized patient-specific surgical instrument on the patient's femur.

In some embodiments, the method may include aligning an alignment slot extending through a body of the customized patient-specific surgical instrument with the visual marking.

In some embodiments, the method may include aligning an alignment slot extending through an arm of the customized patient-specific surgical instrument with the visual marking.

BRIEF DESCRIPTION OF THE DRAWINGS

The detailed description particularly refers to the following figures, in which:

FIG. 1 is a perspective view of a customized patient-specific surgical instrument;

FIG. 2 is a bottom perspective view of the customized patient-specific surgical instrument shown in FIG. 1;

FIG. 3 is a rear elevation view of the customized patient-specific surgical instrument shown in FIG. 1;

FIG. 4 is another bottom perspective view of the customized patient-specific surgical instrument shown in FIG. 1;

FIG. 5 is a top plan view of the customized patient-specific surgical instrument shown in FIG. 1;

FIG. 6 is a front elevation view of the customized patient-specific surgical instrument shown in FIG. 1;

FIG. 7 is a perspective view of distal end of a patient's femur;

FIG. 8 is a perspective view of the customized patient-specific surgical instrument of FIG. 1 positioned on the distal end of the patient's femur of FIG. 7; and

FIG. 9 is an elevation view of the customized patient-specific surgical instrument of FIG. 1 positioned on the distal end of the patient's femur of FIG. 7.

DETAILED DESCRIPTION OF THE DRAWINGS

While the concepts of the present disclosure are susceptible to various modifications and alternative forms, specific exemplary embodiments thereof have been shown by way of example in the drawings and will herein be described in detail. It should be understood, however, that there is no intent to limit the concepts of the present disclosure to the particular forms disclosed, but on the contrary, the intention is to cover all modifications, equivalents, and alternatives falling within the spirit and scope of the invention as defined by the appended claims.

Terms representing anatomical references, such as anterior, posterior, medial, lateral, superior, inferior, etcetera, may be used throughout the specification in reference to the orthopaedic implants and surgical instruments described herein as well as in reference to the patient's natural anatomy. Such terms have well-understood meanings in both the study of anatomy and the field of orthopaedics. Use of such anatomical reference terms in the written description and claims is intended to be consistent with their well-understood meanings unless noted otherwise.

Referring now to FIG. 1, an orthopaedic surgical instrument 10 is shown. The instrument 10 is illustratively a customized patient-specific orthopaedic surgical instrument. What is meant herein by the term “customized patient-specific orthopaedic surgical instrument” is a surgical tool for use by a surgeon in performing an orthopaedic surgical procedure that is intended, and configured, for use on a particular patient. As such, it should be appreciated that, as used herein, the term “customized patient-specific orthopaedic surgical instrument” is distinct from standard, non-patient-specific orthopaedic surgical instruments (i.e., “patient-universal instruments” such as patient-universal cutting blocks) that are intended for use on a variety of different patients and were not fabricated or customized to any particular patient. Additionally, it should be appreciated that, as used herein, the term “customized patient-specific orthopaedic surgical instrument” is distinct from orthopaedic prostheses or implants, whether patient-specific or generic, which are surgically implanted in the body of the patient. Rather, an orthopaedic surgeon uses customized patient-specific orthopaedic surgical instruments to assist in the implantation of orthopaedic prostheses. Examples of “customized patient-specific orthopaedic surgical instruments” include customized patient-specific drill/pin guides, customized patient-specific tibial cutting blocks, customized patient-specific femoral cutting blocks, and customized patient-specific alignment guides.

The customized patient-specific orthopaedic surgical instrument is a femoral cutting guide block 12 in the illustrative embodiment. The anterior contact surfaces and the distal contact surfaces of the cutting block 12 facilitate securing the cutting block 12 on the patient's femur. As described in greater detail below, the surgical instrument 10 is configured to be coupled to the patient's femur in a unique pre-determined location and orientation on the patient's condyles and an anterior portion of the femur extending proximally from the condyles. The cutting block 12 contact regions are configured to couple to the patient's femur in a unique pre-determined location and orientation so that an alignment slot extending through the cutting block 12 is aligned with the deepest portion of the trochlear groove. In the illustrative embodiment, the structure of the cutting block 12 has been contoured to reduce its size relative to conventional cutting blocks and avoid contact with undesirable regions of the patient's bone.

The femoral cutting block 12 includes a base plate 20 and a number of surgical tool guide bodies 22 that are attached to, and extend outwardly from, the base plate 20. In the illustrative embodiment, the femoral cutting block 12 is a single monolithic component formed from a metallic material such as, for example, stainless steel. In that way, the base plate 20 and the guide bodies 22 form a single monolithic metallic block. The femoral cutting block 12 is formed by, for example, Direct Metal Laser Sintering (DMLS), also known as Selective Laser Sintering (SLS), which is a form of additive manufacturing technology. In DMLS, the femoral cutting block 12 is formed in a layer-by-layer fashion using laser sintering in which light fuses metallic powder, forming the metallic structures that define the femoral cutting block 12. It should be appreciated that other forms of additive manufacturing technology such as, for example, optical fabrication, photo-solidification, or resin printing may be used to fabricate the femoral cutting block 12.

The base plate 20 includes a pair of arms 24, 26 that are configured to engage the distal end 18 of the patient's femur 16 (see FIG. 7). The arms 24, 26 are spaced apart from each other such that a notch 28 is defined between the inner edges of the arms 24, 26. The notch 28 is sized and shaped to correspond to the natural intercondylar notch 30 of the patient's femur 16, which is defined between the natural condyles 32, 34 of the patient's femur 16 (see FIG. 7).

Each of the arms 24, 26 has a bone-contacting or bone-facing surface 36 (shown in FIG. 2) that engages one of the natural condyles 32, 34. In the illustrative embodiment, each bone-facing surface 36 includes a number of negative contours 38 that are configured to receive a portion of the natural condyles 32, 34. Each contour 38 has a unique set of ridges 40 and depressions 42 that are shaped to engage a corresponding unique set of depressions 44 and ridges 46 of the natural femoral condyles 32, 34 (see FIG. 7). Each of the arms 24, 26 also includes an outer surface 48 that is positioned opposite its corresponding bone-facing surface 36. In the illustrative embodiment, each outer surface 48 is substantially smooth. As used herein, the term “substantially” should be understood to refer to the normal tolerances created by manufacturing variation and other design criteria. As such, a “substantially smooth surface” is one that is smooth within the normal tolerances created or permitted by manufacturing variation and other design criteria.

The base plate 20 also includes a proximally extending arm 50 that is configured to engage the distal end 18 of the patient's femur 16. The proximally extending arm 50 includes a trunk 86 and a flange 88 extending proximally from the trunk 86. The trunk 86 includes a base 92 having first width 94 between a pair of edges 66, 68. The trunk 86 extends proximally and narrows to a point 78 that has a width 130 that is less than the width 94. From the point 78, the trunk 86 flares outward to an end 132 having a width 134 that is greater than the width 130 and less than the width 94. From the point 78 to the end 132, the trunk 86 curves laterally to mimic the curve of the trochlear groove 166. The trunk 86 is generally concave such that the point 78 extends anteriorly of the base 92 and the end 132. The trunk 86 also includes convex and concave portions to receive corresponding concave and convex portions of the patient's femur 16.

The trunk 86 of the proximally extending arm 50 includes a bone-facing surface 52 (shown in FIG. 2) that includes a number of negative contours 54 that are configured to receive a portion of the patient's femur 16. The bone-facing surface 52 extends across the trunk 86 from the base 92 to the end 94. The contour 54 of the trunk 86 has a unique set of ridges 56 and depressions 58 that are shaped to engage a corresponding unique set of depressions 60 and ridges 62 of the patient's femur 16. The proximally extending arm 50 also includes an outer surface 64 that is positioned opposite the bone-facing surface 52. In the illustrative embodiment, the outer surface 64 is substantially smooth.

The trunk 86 is configured to curve with the trochlear groove 166 of the patient's femur 16. As illustrated in FIG. 7, the trochlear groove 166 extends between the natural femoral condyles 32, 34 and ends at an anterior surface 168 of the femur 16, which begins at an end of the natural femoral condyles 32, 34. That is, the natural femoral condyles 32, 34 curve into the anterior surface 168. The trochlear groove 166 also curves laterally between the natural femoral condyles 32, 34. The trunk 86 is configured to follow the path of the trochlear groove 166 so that the flange 88 engages the anterior surface 168 of the patient's femur 16.

The flange 88 extends proximally from the trunk 86 and includes a pair of arms 136 that extend medially and laterally from the trunk 86. The posterior edges 66, 68 extend along the trunk 86 and flange 88. As a result, each of the edges 66, 68 includes convex and concave portions to receive corresponding concave and convex portions of the patient's femur 16. The edges 66, 68 extend around the arms 136 of the flange and meet at a posterior tip 69 that is sized and shaped to be positioned on the anterior surface 168 of the patient's femur 16. The flange 88 includes a bone-facing surface 96 that includes a number of negative contours 98 that are configured to receive a portion of the anterior surface 168 of the patient's femur 16. The contour 98 of the flange 88 has a unique set of ridges 70 and depressions 72 that are shaped to engage a corresponding unique set of depressions 74 and ridges 76 of the anterior surface 168 of the patient's femur 16. The negative contours 38, 54, 98 of the base plate 20 permit the cutting block 12 (and hence the tool guide bodies) to be positioned on the patient's femur 16 in a unique pre-determined location and orientation.

In the illustrative embodiment, the base plate 20 of the cutting block 12 has a low-profile to reduce the size of the incision and reduce the amount of bone displacement needed to position the cutting block 12. The low-profile has been customized for block 12 by minimizing the thicknesses of the arms 24, 26 and the proximally extending arm 50. A thickness 82 is defined between the outer surface 48 and the bone-facing surface 36 of each arm. To minimize the thickness 82, the outer surface 48 of each arm is convexly curved to follow the concave curvature of the bone-facing surface 36. Similarly, a thickness 84 is defined between the outer surface 64 and the bone-facing surface 52 of the proximally extending arm 50, and the outer surface 64 of the arm 50 is shaped to follow the geometry of the bone-facing surface 52 to minimize the thickness 84.

Each of the surgical tool guide bodies 22 of the cutting block 12 is attached to and extends outwardly from the outer surfaces 48, 64 of the arms 24, 26 and the proximally extending arm 50 to a free end 90 that is spaced apart from the base plate 20. In the illustrative embodiment, the guide bodies 22 include an anterior guide body 100 that extends anteriorly from the anterior ends of the arms 24, 26 and the proximally extending arm 50 to its free end 102. The anterior guide body 100 includes a distal flange 104 and a pair of bosses 106, 108 that extend proximally from the flange 104.

The distal flange 104 of the anterior guide body 100 includes an elongated opening 110 that is defined in the free end 102 and a number of inner walls 112 that extend inwardly from the opening 110. As shown in FIG. 3, the inner walls 112 extend to another opening 114 that is defined in the bone-facing surface 52. The opening 114 extends through the contour 54 of the base plate 20 such that the opening 114 is defined by the edges 66, 68 of the bone-facing surface 52, which follow a curved, irregular path that matches the shape of the patient's femur 16 in that region. The opening 114 cooperates with the inner walls 112 and the elongated opening 110 to define the guide slot 98, which is sized and shaped to guide a surgical tool such as, for example, a cutting blade, into engagement with the patient's bone. As described above, the cutting guide slot 98 is positioned to guide a customized, patient-specific resection of the distal end 18 of the patient's femur 16. Because the edge 66 follows the shape of the patient's femur 16 and the posterior tip of the edge 66 extends into the patient's trochlear groove, the cutting guide slot 98 provides support for the cutting blade in close proximity to the region under resection.

As shown in FIG. 1, each of the bosses 106, 108 extend from a proximal surface 116 of the distal flange 104 to a curved proximal end 118. It should be appreciated that in other embodiments one or both of the bosses 106, 108 may be spaced apart from the distal flange 104, thereby forming separate guide bodies. An opening 120 is defined in the free end 102 of each of the bosses 106, 108 adjacent to the proximal end 118. An inner wall 122 extends inwardly from the opening 120. As shown in FIG. 4, each inner wall 122 extends to another opening 124 to define a guide slot 126 extending through the cutting block 12. In the illustrative embodiment, each guide slot 126 is a drill guide and fixation pin guide hole, which is sized and shaped to guide a surgical drill to prepare the patient's bone to receive a fixation pin to couple the block 12 to the bone.

The guide bodies 22 include a pair of posterior guide bosses 140, which are attached to, and extend distally from, the outer surfaces 48 of the arms 24, 26, respectively. Each posterior guide boss 140 includes a guide slot 142 that is sized and shaped to guide a surgical drill and a fixation pin into engagement with the patient's bone to couple the block 12 to the bone. Each guide boss 140 includes a post 144 that extends from a base 146 attached to the outer surface 48 of one of the arms 24, 26 to a free end 148 that is spaced apart from the outer surface 48.

An opening 154 is defined in the free end 148 of each boss 140. An inner wall 178 extends inwardly from the opening 154 to another opening 158 (shown in FIG. 2) that is defined in a bone-facing surface 36 of one of the arms 24, 26. The openings 154, 158 and the inner wall 178 cooperate to define the guide slot 142. As described above, each guide slot 142 is a drill guide and fixation pin guide hole, which is sized and shaped to guide a surgical drill or self-drilling fixation pin to prepare the patient's bone to receive a fixation pin to couple to the block 12 to the bone.

Referring to FIGS. 5-6, the base plate 20 includes an alignment slot 200 positioned to align with a deepest portion of the patient's natural trochlear groove 166. The distal flange 104 has a planar distal surface 202 and a planar proximal surface 204 (shown in FIG. 4). A distal end 210 of the alignment slot 200 is defined by inner walls 208 extending between an opening 206 in the distal surface 202 and an opening in the inner walls 112 of the elongated opening 110. The distal end 212 of the alignment slot 200 is also defined by inner walls 230 extending between an opening in the inner walls 122 of the elongated opening 110 and an opening 212 in the proximal surface 204. The distal end 210 of the alignment slot 200 extends transverse to the cutting guide slot 98.

The bone-facing surface 52 of the trunk 86 of the proximally extending arm 50 forms a posterior surface 214 of the trunk 86, and the outer surface 64 forms an anterior surface 216 (shown in FIG. 1) of the trunk 86. A proximal end 220 of the alignment slot 200 is defined by inner walls 218 extending between an opening 222 in the posterior surface 214 and an opening 224 in the anterior surface 216. The proximal end 220 of the alignment slot 200 extends transverse to the cutting guide slot 98. In the illustrative embodiment, the proximal end 220 of the alignment slot 200 is curved both laterally and in a concave shape to match a contour of the trunk 86 and the deepest portion of the patient's natural trochlear groove 166. The distal end 210 and the proximal end 220 of the alignment slot 200 extend from one another to form a continuous alignment slot 200 that is transverse to the cutting guide slot 98.

Prior to surgery, a three-dimensional model of the patient's femur 16 is developed based on scans of the patient's femur 16. The scans may include a magnetic resonance image, a computed tomography image, a plurality of x-ray images, or the like. The cutting block 12 is manufactured to include negative contours that match the positive contours of the three-dimensional model. Additionally the alignment slot 200 is formed in the cutting block 12 to match the position of the deepest portion of the patient's natural trochlear groove 166. Creating the cutting block 12 based on the three-dimensional model facilitates ensuring a correct alignment of the cutting block 12 on the patient's femur 16.

Referring now to FIG., 7, during use, a surgeon prepares the patient's femur 16 by placing a visual indicator 250 on the deepest portion of the patient's natural trochlear groove 166. In the illustrative embodiment, the visual indicator 250 is a line drawn on the deepest portion of the patient's natural trochlear groove 166. The cutting block 12 is then positioned on a distal end 18 of the patient's femur 16 so that the unique set of ridges 40 and depressions 42 engage the corresponding unique set of depressions 44 and ridges 46 of the natural condyles 32, 34 and the unique set of ridges 56 and depressions 58 engage the corresponding unique set of depressions 60 and ridges 62 of an anterior side 254 of the patient's femur 16. The unique set of ridges 70 and depressions 72 of the flange 88 are also positioned to engage the corresponding unique set of depressions 74 and ridges 76 of the anterior surface 168 of the patient's femur 16.

The surgeon verifies the alignment of the cutting block 12 on the femur 16 by aligning the visual indicator 250 with the alignment slot 200. As illustrated in FIG. 8, the proximal end 220 of the alignment slot 200 is aligned with a portion of the visual indicator 250 that extends along the anterior side 254 of the patient's femur. As illustrated in FIG. 9, the distal end 210 of the alignment slot 200 is aligned with a portion of the visual indicator 250 that extends along the distal end 18 of the patient's femur 16 and extends between the natural condyles 32, 34.

The surgeon can then position a fixation pin in each of the guide slots 126 and 142 to secure the cutting block 12 to the patient's femur. A distal resection is then performed on the distal end 18 of the patient's femur 16 by advancing a surgical saw through the guide slot 98. In some embodiments, the fixation pins inserted through the guide slots 142 may be removed before the distal resection of the distal end 18 of the patient's femur 16 so that the fixation pins do not interfere with the surgical saw.

While the disclosure has been illustrated and described in detail in the drawings and foregoing description, such an illustration and description is to be considered as exemplary and not restrictive in character, it being understood that only illustrative embodiments have been shown and described and that all changes and modifications that come within the spirit of the disclosure are desired to be protected.

There are a plurality of advantages of the present disclosure arising from the various features of the devices and assemblies described herein. It will be noted that alternative embodiments of the devices and assemblies of the present disclosure may not include all of the features described yet still benefit from at least some of the advantages of such features. Those of ordinary skill in the art may readily devise their own implementations of the devices and assemblies that incorporate one or more of the features of the present invention and fall within the spirit and scope of the present disclosure as defined by the appended claims. 

1. An orthopaedic surgical instrument, comprising: a customized patient-specific surgical instrument comprising: a body, a cutting guide slot extending through the body, a pair of first arms extending posteriorly from the body, each arm including a first customized patient-specific negative contour configured to receive a portion of a first corresponding positive contour of one of a patient's femoral condyles, a second arm extending proximally from the body, the second arm having a second customized patient-specific negative contour configured to receive a portion of a second corresponding positive contour of an anterior surface of the patient's femur, and an alignment slot extending through the body and the proximally extending arm and positioned to align with a deepest portion of a trochlear groove of the patient's femur when the customized patient-specific surgical instrument is positioned on the patient's femur.
 2. The orthopaedic surgical instrument of claim 1, wherein the alignment slot extends transverse to the cutting guide slot.
 3. The orthopaedic surgical instrument of claim 1, wherein the body has a planar distal surface and a planar proximal surface, the alignment slot including an opening extending through the distal surface and an opening extending through the proximal surface.
 4. The orthopaedic surgical instrument of claim 1, wherein the second arm includes a trunk extending from the body and a flange attached to a proximal end of the trunk, wherein the flange includes a portion of the second customized patient-specific negative contour.
 5. The orthopaedic surgical instrument of claim 4, wherein the trunk includes an anterior surface and a posterior surface, wherein the alignment slot includes an opening extending through the anterior surface and an opening extending through the posterior surface.
 6. The orthopaedic surgical instrument of claim 5, wherein the opening extending through the anterior surface and the opening extending through the posterior surface are curved.
 7. The orthopaedic surgical instrument of claim 1, wherein the customized patient-specific surgical instrument includes a boss attached to, and extending from, the body to a free end spaced apart from the body, the boss including an opening that is defined in its free end.
 8. The orthopaedic surgical instrument of claim 7, including a guide hole extending through the boss.
 9. An orthopaedic surgical instrument, comprising: a customized patient-specific surgical instrument comprising: a body, a cutting guide slot extending through the body, a pair of first arms extending posteriorly from the body, each arm including a first customized patient-specific negative contour configured to receive a portion of a first corresponding positive contour of one of a patient's femoral condyles, and an alignment slot extending through the body transverse to the cutting guide slot and positioned to align with a deepest portion of a trochlear groove of the patient's femur when the customized patient-specific surgical instrument is positioned on the patient's femur.
 10. The orthopaedic surgical instrument of claim 9, wherein the body has a planar distal surface and a planar proximal surface, the alignment slot including an opening extending through the distal surface and an opening extending through the proximal surface.
 11. The orthopaedic surgical instrument of claim 9, wherein the customized patient-specific surgical instrument includes a boss attached to, and extending from, the body to a free end spaced apart from the body, the boss including an opening that is defined in its free end.
 12. The orthopaedic surgical instrument of claim 11, including a guide hole extending through the boss.
 13. The orthopaedic surgical instrument of claim 9, including a second arm extending proximally from the body, the second arm including a trunk extending from the body and a flange attached to a proximal end of the trunk.
 14. The orthopaedic surgical instrument of claim 13, wherein the second arm has a second customized patient-specific negative contour configured to receive a portion of a second corresponding positive contour of an anterior surface of the patient's femur.
 15. The orthopaedic surgical instrument of claim 14, wherein the flange includes a portion of the second customized patient-specific negative contour.
 16. The orthopaedic surgical instrument of claim 13, wherein the trunk includes an anterior surface and a posterior surface, wherein the alignment slot includes an opening extending through the anterior surface and an opening extending through the posterior surface.
 17. The orthopaedic surgical instrument of claim 16, wherein the opening extending through the anterior surface and the opening extending through the posterior surface are curved.
 18. A method of performing an orthopaedic surgical procedure, the method comprising: placing a visual marking on a surface defining a deepest portion of a trochlear groove of a patient's femur, placing a customized patient-specific surgical instrument on the patient's femur, and aligning an alignment slot extending through the customized patient-specific surgical instrument with the visual marking on the surface of the patient's femur to position the customized patient-specific surgical instrument on the patient's femur.
 19. The method of claim 18 including aligning an alignment slot extending through a body of the customized patient-specific surgical instrument with the visual marking.
 20. The method of claim 18 including aligning an alignment slot extending through an arm of the customized patient-specific surgical instrument with the visual marking. 